This page is about the ability to see things. For, the religious experience see Visions.

Vision (or visual perception) is the ability to interpret visible light information reaching the eyes which is then made available for planning and action. The resulting perception is also known as eyesight, or simply sight (adjectival form: visual, optical, or ocular). The various components involved in vision are known as the visual system. Many expressions refer to vision as an indication of shared perceptions or conceptions, especially in the context of the future and strategic planning; such use of the word also usually refers to discernment of long term views and consequence of many things, rather than such aspects and appearances as are immediately apparent and obvious to most people.

You’re actually socially isolating yourself with your phone. I feel like it’s kind of emasculating. This Google Glass really takes away that excuse.… It really opened my eyes to how much of my life I spent secluded away in email or social posts. My vision when we started Google 15 years ago was that eventually you wouldn’t have to have a search query at all — the information would just come to you as you needed it. This is the first form factor that can deliver that vision.

The Greeks elaborated several theories of vision. According to the Pythagoreans, Democritus, and others vision is caused by the projection of particles from the object seen, into the pupil of the eye. On the other hand Empedocles, the Platonists, and Euclid held the strange doctrine of ocular beams, according to which the eye itself sends out something which causes sight as soon as it meets something else emanated by the object.

Not so many years ago this was a mistake that brainscientists actually made: they succumbed all too often to the temptation to treat vision as if it were television — as if it were simply a matter of getting "the picture" from the eyes to the screen somewhere in the middle where it could be handsomely reproduced so that the phenomena of appreciation and analysis could then get underway. Today we realize that the analysis — the whatever you want to call it that composes, in the end, all the visual understanding — begins right away, on the retina; if you postpone consideration of it, you misdescribe how vision works.

In the Middle Ages society was far more static and was essentially hierarchical in nature. As a result the causal or genetic attitude was far less important in medieval thought that it is in ours and the concept of evolution had little influence compared with the role of symbolism in the general world-view... Moreover, even the concept of time itself was of less significance to historians... For St Augustine the date of an event was of far less importance than its theological significance. His tendency to see everything in a theological rather than in a historical perspective was a powerful influence in the Middle Ages... It was not until the nineteenth century that the fundamental significance of the historical perspective came to be generally recognized. This was several hundred years after the theory and practice of perspective had been developed by painters and others. In each case a new way of looking at the world resulted.